American historian Alexander B. Rossino examines the first month of World War II, September/October 1939 - Germany's conquest of Poland - when the world was shown, but never fully appreciated, the indelible Nazi program in store for those living to Germany's east: Poles, Ukrainians, Belarusans, Russians, inhabitants of the Baltic states and, of course, Jews.

His account shows conclusively, among other things, that the way Hitler implemented his 1941 invasion of his erstwhile ally, Stalin's Soviet Union, was a larger scale re-run of the 1939 Polish campaign.

Despite many published Polish-language accounts of Hitler's so-called September Campaign, most Western historians have never fully grasped the new type of racial-ideological warfare that began on day one of World War II.

But after more than six decades, Rossino corrects this omission.

He writes: "The attack [upon Poland], Hitler insisted, should devastate Poland so thoroughly that it could not 'be taken into account as a political factor for the next few decades'.

"Although Hitler tended toward hyperbole when speaking about military operations, the level of violence he demanded in this case was not exaggeration. Rather, it was a genuine expression of the brutality which he wanted from his armed forces and SS towards war against the Poles.

"And as the five-week war in Poland took its course, it became clear that Hitler's wish had been granted. The German army and SS conducted the Polish campaign with a viciousness that was unprecedented in the annals of European conflict up to that point."

Poland's conquest was undertaken not only by Hitler's army (Wehrmacht) and air force (Luftwaffe) but, equally significantly, by specially-created SS killing groups, the Einsatzgruppen.

The groups were greatly assisted in their designated missions against civilians (Jewish and Gentile), both by the German army and by members of Poland's ethnic German minority (Volksdeutsche) who had helped draw up lists naming those who should be promptly eliminated.

One reason the nature of Poland's conquest wasn't fully appreciated, despite what members of the Polish government-in-exile in London from 1940 to 1945 claimed and highlighted, was that it differed so markedly from what British, French, Dutch, and Belgian captives and escapees experienced after the fall of France and the Low Countries.

However, all that this proved was that Hitler's successful eastern and western onslaughts of 1939-1940 were implemented differently, and deliberately so.

The European theatre of World War II was in fact two markedly different wars.

In the West there was a traditional encounter, similar to that experienced during the 1870-71 Franco-Prussian War, and, apart from the long stalemate of the Great War's trench warfare, somewhat akin to that conflict too.

Not so in the East where, even before Poland's Jews were forced into ghettos and slowly starved before the implementation of the genocidal Aktion Reinhardt, both Jews and Gentiles were regularly and often summarily executed by Einsatzgruppen firing-squads.

Rossino's chapter, "The German army and the opening phase of Tannenberg", is probably the first such detailed English-language account of this huge killing operation against Polish intellectuals, scholars, teachers, journalists, priests and veterans.

Preparation for Operation Tannenberg (Unternehmen Tannenberg) was well underway before the outbreak of war with preparation of lists containing names of some 60,000 Polish individuals, compiled with the assistance of German fifth-columnists inside the country.

Rossino's account has the crucial advantage of being based on study and analysis of German units' diaries and other contemporary records.

He writes: "Consequently, the SS murder campaign escalated precipitously throughout the autumn and early winter of that year until by December 1939 the SS and their ethic German auxiliaries had slaughtered as many as 50,000 people. At least 7,000 of these victims were Polish Jews.

"The roughly 4-to-1 ratio of Polish Christian deaths to Polish Jewish deaths suggests a decidedly anti-Polish and not anti-Jewish animus of the killing program of the SS in those early months of the war."

When Tannenberg-style mass killings were repeated with the invasion of the Soviet Union (Operation Barbarossa), "the targets of the killers' gun-sights had ... shifted decisively to the Jews".

This leads Rossino to conclude that the predominant 1939 killings of Poles "served as a kind of dress-rehearsal for the initial wave of murder that later engulfed Soviet Jewry during the opening phase of Operation Barbarossa".

Nothing like Tannenberg and Barbarossa was experienced under Hitler's campaigns in France and the Low Countries.

The only other theatre to experience such killings was the fragmenting state of Yugoslavia, Europe's other Slavic quarter, when it was under German and Italian occupation. Yugoslavia, of course, had its own set of unique politically disparate characteristics.

Rossino concludes: "[T]he brief war with Poland in September 1939 was the first step in the overall escalation of National Socialist racial and occupation policies during World War II that ultimately resulted in genocide."